Antigen-presenting cells (APCs) can induce tolerance or immunity. We describe a subset of human APCs that express indoleamine 2,3-dioxygenase (IDO) and inhibit T cell proliferation in vitro. IDO-positive APCs constituted a discrete subset identified by coexpression of the cell-surface markers CD123 and CCR6. In the dendritic cell (DC) lineage, IDO-mediated suppressor activity was present in fully mature as well as immature CD123+ DCs. IDO+ DCs could also be readily detected in vivo, which suggests that these cells may represent a regulatory subset of APCs in humans.

SUMMARY:The mechanism by which the immune system of a tumor-bearing host acquires tolerance toward tumor antigens is still elusive. Antigen-presenting cells (APCs) are critical regulators of the decision between immune response and tolerance. APCs that express the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) have been found to inhibit T-cell responses both in vitro and in vivo. We hypothesized that malignant tumors exploit this mechanism by recruiting IDO-expressing APCs to the tumor-draining lymph nodes. To test this hypothesis, archival tissues and records of 26 cases of lymph node dissection for invasive cutaneous melanoma were obtained. IDO immunohistochemistry was performed on 14 cutaneous tumors and 328 regional lymph nodes. Abnormal accumulations of IDO-positive cells with a monocytoid or plasmacytoid morphology were identified in the perisinusoidal regions of draining lymph nodes in 45% of nodes studied. Recruitment of IDO-positive cells was seen in nodes with and without malignancy. We hypothesize that these IDO-positive APCs may contribute mechanistically to acquired tolerance to tumor antigens. Immunostaining of tumor-draining lymph nodes for abnormal accumulation of IDOexpressing cells might thus constitute an adverse prognostic factor and could contribute to the decision process and the appropriate care of patients with this deadly disease. (Lab Invest 2003, 83:1457-1466.

Many chemotherapy drugs are known to cause significant clinical neurotoxicity, which can result in the early cessation of treatment. To identify and develop more effective means of neuroprotection it is important to understand the toxicity of these drugs at the molecular and cellular levels. In the present study, we examine the effects of paclitaxel (taxol), cisplatin, and methotrexate on primary rat neurons including hippocampal, cortical, and dorsal horn/dorsal root ganglion neuronal cultures. We found that all of these anti-cancer drugs induce substantial neurotoxicity evidenced by neurite degeneration. The neurons are capable of recovering after treatment withdrawal, but taxol exerts a biphasic effect that results in the collapse of processes days after treatment is withdrawn. After cisplatin and methotrexate treatment, we observed the degeneration of neuronal processes including the reduction of dendritic branching, length, and altered growth cone formation, indicating an abnormal arrangement of the actin cytoskeleton consistent with the involvement of Rho family small GTPases. Inhibiting RhoA downstream effector p160 ROCK /Rho kinase using Y-27632, or activating p75 neurotrophin receptor (p75 NTR ) using non-peptide mimetic LM11A-31, were able to reverse the degeneration caused by cisplatin and methotrexate. Therefore, the neurotoxicity resulting from exposure to the anti-cancer drugs cisplatin and methotrexate can be alleviated by inhibiting Rho signaling pathway.

The association of sickle cell trait (SCT) and hereditary spherocytosis (HS) has been reported in only 18 patients. Three of these 18 patients experienced splenic infarct or acute splenic sequestration. We report here a 46-year-old African-American male, the oldest reported case to date, who experienced episodes of hemolysis and severe left upper quadrant pain for the past 26 years. The patient had compensated hemolysis with splenomegaly. A CT scan of the abdomen revealed a large infarct in the spleen. The diagnosis of SCT was confirmed with isoelectric focusing, cation exchange and reverse-phase HPLC. The presence of a silent, interacting globin variant as the cause of hemolysis and sickling in the spleen was ruled out by sequencing of the α1-, α2- and β-globin genes. The diagnosis of HS was established by an osmotic fragility test. The interaction of HS and SCT leads to RBC dehydration with increased MCHC and intracellular Hb S concentration presumably favoring intrasplenic sickling and resultant splenic infarcts and sequestration as seen in this case.

While high-dose bolus inpatient interleukin-2 is generally given on 8-week cycles, continuous infusion interleukin-2 could potentially allow for more rapidly repeated cycles. Fourteen (14) patients with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1, having either kidney cancer (6) or melanoma (8), have been treated with continuous infusion (CIV) interleukin-2 (IL-2) 18 MIU/m(2)/24 hours for 72 hours. Cycles were repeated every 3 weeks up to 4 cycles, then every 3-4 weeks for 2 cycles, then every 6-8 weeks, until progression or intolerable toxicity. All patients received famotidine 20 mg intravenously (i.v.) twice per day during the 72-hour infusions. Patient characteristics included a median ECOG performance status of 1; median age = 63 (range: 25-79); most common metastatic sites: lung (9), bone (5), lymph nodes (5), and the liver (3). No patients with metastatic kidney cancer underwent a nephrectomy prior to interleukin-2. Median number of cycles received = 5 (1-9). No patients required Intensive Care Unit (ICU) admission. There have been no treatment-related deaths. Most common toxicities have been rigors, fever, nausea/emesis, and the reversible elevation of creatinine. One complete response and three partial responses (67% response rate; 95% confidence interval: 30%-90%) have been seen in kidney cancer, and two partial responses (25% response rate; 95% confidence interval: 7%-60%) have occurred in melanoma. Median survival has not been reached at >9+ months. Responding sites include the liver, bone, lung, lymph node and subcutaneous sites. Inpatient 72-hour continuous infusion interleukin-2 at this dose and schedule is well tolerated by patients with an ECOG performance status of 0 or 1 and has activity in kidney cancer and melanoma.